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Orientation based on vector

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Jonathan Cutrell
Orientation based on vector
on Sep 16, 2009 at 5:43:49 pm

Hello all,

Not sure if this is just something I'm completely missing...

I am trying to decide the orientation of an object by the direction it is traveling across 3d space. So in other words, if the object is traveling only on the z axis (say from 0 to -4000) the object would be facing the direction it is traveling. This wouldn't be so hard - the challenging part is if you are going from 360, 240, 0 to 100, 600, 500. This would be a diagonal line. And the even more challenging part to me is if you are interpolating with any kind of curve.

The way I have it set up, I am wanting to animate an object with wiggle(1, 800). With this expression, the object moves with smooth interpolation, and therefore to achieve this goal the object's orientation would have to interpolate at the same rate. I am guessing there is some way to do this through expressions? I know it will be a challenge, because expressions cannot pass on information from previous frames. Is it possible to auto-keyframe based on an expression, and then use the differences in the values to find a vector value, and then calculate the orientation?


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Dave LaRonde
Re: Orientation based on vector
on Sep 16, 2009 at 5:57:55 pm

How about simply using the Orient Along Path command for the layer? If it looks goofy, you simply play with the the layer's Orientation until it's right.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Dave LaRonde
Re: Orientation based on vector
on Sep 16, 2009 at 7:23:00 pm

[Jonathan Cutrell] "...I am wanting to animate an object with wiggle(1, 800). With this expression, the object moves with smooth interpolation..."

I missed that one earlier. Why use an expression if you want smooth interpolation, by which I assume you mean ramping up to speed, and ramping down in speed to a stop?

All you need is to highlight the beginning and ending keyframes, right click and use the contextual menu to apply Easy Ease. It's a lot easier than an expression.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Jonathan Cutrell
Re: Orientation based on vector
on Sep 16, 2009 at 8:20:01 pm

I should probably explain myself a bit better...

I am animating a null object and tying particular to the null. I'm not using a light because it creates problems with using other lights with Particular 2 (the light is accepted not only as the emitter but as a light would normally be accepted). The particle I am using is a custom particle (a few circles precomped). Using it to build a mesh of "strings", but this could be any shape really.

All of this is fine and well; The particle, however, stays oriented to the camera at all times. Is there a way to tie the orientation along the path to define the orientation of the custom particle layer within the particle precomp? I imagine it would require the layer to be 3d within the precomp.


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